Etch resistant alumina based coatings

ABSTRACT

Method of forming a protective hard mask layer on a substrate in a semiconductor etch process, comprising the step of applying by solution deposition on the substrate a solution or colloidal dispersion of an alumina polymer, said solution or dispersion being obtained by hydrolysis and condensation of monomers of at least one aluminum oxide precursor in a solvent or a solvent mixture in the presence of water and a catalyst. The invention can be used for making a hard mask in a TSV process to form a high aspect ratio via a structure on a semiconductor substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates byreference essential subject matter disclosed in International PatentApplication No. PCT/FI2010/050246 filed on Mar. 29, 2010.

BACKGROUND OF THE INVENTION

Field of Invention

The following disclosure relates to the manufacturing of microelectronicdevices, specifically but not exclusively to layers which enable theformation structures on a substrate using photolithographic techniques.In particular, the invention relates to the methods of producingmaterials and coatings which can be used in photolithographicapplications and their subsequent etching processes to form desiredstructures on a substrate, and applications thereof.

Description of Related Art

To meet the demand for smaller electronic products, there is acontinuing effort to increase the performance of packagedmicroelectronic devices while simultaneously minimizing the area of suchdevices on printed circuit boards.

In continued miniaturization, reducing the height and the surface areasize i.e. the density of high performance devices is difficult. A methodfor increasing the component density of microelectronic devices, inaddition to reduced line widths, is to lay one device or integratedcircuit (IC) on top of another. In practice, this is achieved byelectrically coupling an active circuit layer on a die to another activecircuit layer on the same, or a different, die by means of anelectrically conductive through substrate vias. In semiconductorindustry such are most frequently called through silicon vias (TSV).

These vertical interconnects electrically couple bond-pads or otherconductive elements adjacent or nearby to one side of the dies toconductive elements adjacent or nearby to the other side of the dies.Working through the back-end-of-the-line (BEOL) or the “via lastmethod”, through silicon wafer interconnects, for example, areconstructed by forming deep vias from the backside to bond-pads on thefront side of the wafer, which contains most of the circuitry for thegiven design. The formed vias are often closed at one end, then filledwith a conductive material, and after further processing the wafer inits manufacturing flow, it is eventually thinned to reduce the thicknessof the final dies sufficiently to obtain a through substrateinterconnect. Working though the front-end-of-the-line (FEOL) or the“via first method” the vias are formed to great extent prior to themanufacturing of designed circuitry. The “via last method” is morechallenging as the vias in general are much deeper compared to thosegenerated in the “via first method” and the formation of these includeetching or laser processing through stacks of layers such as silicon andsilicon oxide.

A complexity in the formation of through-substrate interconnects is inthe difficulty to perform etching to give such deep, narrow holes in asubstrate. These high aspect ratio vias are often formed on substrates0.75-1.5 mm thick and should exhibit minimum amount of sidewallroughness to permit successful subsequent manufacturing steps. Theclosed vias can be formed by etching the holes through a patterngenerated by photo lithographic techniques. The etching is predominatelycarried out in inductive coupled plasma (ICP) reactors where theconditions to form such vias may require considerable amount of time.Additionally, the depth of the holes is difficult to control and theetchant may damage features on substrate unless properly protected.

The vias may also be formed by laser processing holes into thesubstrate. Laser processing of high aspect ratio vias through thesubstrate is not suitable for many applications. The depths of the holesare difficult to control resulting in too shallow or deep vias. Laserprocessing is also a high temperature process producing hot zones whichmay affect neighboring structures within the wafer and requires producedresidues to be removed. Hence, etching or laser processing deep, highaspect ratio holes in a substrate may be difficult in many applications.

A second complexity in the formation of the deep, high aspect ratiostructures is in the pattern integrity of the structure. The patterningfor a given layer is often performed by a multi-step process consistingof photo resist spin coating, photo resist exposure, photo resistdevelopment, substrate etch, and photo resist removal of a substrate.Performing etching of deep vias may require very thick photo resistduring etching as the environment may cause undesirable degradation ofthe photo resist as well. Hence, difference in etch rates should be aslarge as possible between the substrate to be etched and the coatingpreventing the undesired etching of the substrate. Additionally,application of such thick resists may be impractical in terms of timeconsumed and contamination of the ICP reactor that result from the useof such thick resists. Hence the selectivity of etching of the resistused in patterning and the substrate is of great importance.

In addition, materials or hard masks, with high etch selectivity havebeen employed in photolithographic formation of features with a linewidth of 65 nm and below. As variations in line widths of the patternsduring photolithographic processing can result from optical interferencefrom light reflecting off an underlying layer on a semiconductorsubstrate, anti-reflective coatings (ARC) have been employed to avoidthis effect. To minimize the required processing steps it is beneficialto combine the properties of the hard mask layer and the ARC in a singlelayer. As regards the state of the art, reference is made to USPublished Patent Application No. 2008/0206578.

In view of the drawbacks with prior art in patterning and etching ofmaterials to enable formation of deep, high aspect ratio structures andnarrow line widths, there is a continued need to develop novel materialswhich substantially reduce degradation of the pattern forming material,improve the protection of laid out designs on a substrate and improvethe manufacturing efficiency and control of deep, high aspect ratio, andother vias, holes and structures.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide new compositions forapplications requiring a highly etch resistant hard mask, whichsufficiently maintains its thickness and properties in environments usedfor etching desired substrates in semiconductor manufacturing processes.

Another object of the present invention is to provide new materialcompositions based on aluminum oxide polymers and copolymers of aluminumand organosilicon oxides that meet the requirements for a hard mask.

A further object of the present invention is to provide a method for thepreparation of a hard mask coating on a substrate.

A fourth object of the present invention is to provide a solvent systemwhich stabilizes the aluminum oxide polymers and copolymers of aluminumand organosilicon oxides sufficiently to permit long shelf life withoutadverse limitations on its performance.

A further objective is to provide hard mask according to the inventionthat also functions as an anti-reflection coating and hard mask (etchmask) in the semiconductor or in particular in TSV process. By theanti-reflection coating according to the innovation we mean that thehard mask also functions as a bottom anti-reflection coating.

One more objective is to provide a layer in integrated circuits whichpossesses a coefficient of thermal expansion (CTE) value close to thatof silicon.

Finally, it is an object to provide materials with so good opticalproperties that they will enable good lithographic processing, but alsonon-sacrificial nature of the film meaning that the hard mask may have apermanent optical function in the device.

These and other objects, which jointly with existing materials andmethods are achieved by this present invention are claimed and describedherein.

The present invention is based on the idea of forming a protective hardmask layer on a substrate in a semiconductor etch process, comprisingthe step of applying by solution deposition on the substrate a solutionor colloidal dispersion of an alumina polymer, said solution ordispersion being obtained by hydrolysis and condensation of monomers ofat least one aluminium oxide precursor in a solvent or a solvent mixturein the presence of water and a catalyst.

In particular, the preferred alumina precursors have the general formulaof eitherAlX_(n)(OR¹)_(3-n)wherein

-   R¹ is independently selected from the group of hydrogen, linear    alkyl, branched alkyl, cyclic alkyl, and aryls;-   X is independently chosen from a group consisting of chloro, bromo,    iodo, ester groups, in particular acyl, sulphate, sulfide, and nitro    groups,-   n is an integer which varies between 0-3,-   or    (R²)_(m)AlX_(n)(OR¹)_(2-n)    wherein-   R¹ is independently selected from the group of linear alkyl,    branched alkyl, cyclic alkyl, and aryl;-   R² is independently selected from group of carboxylic acids,    α-hydroxy carboxylic acids, carboxylic acid salts, beta-diketones,    esters and beta-ketoesters;

More specifically, the present invention is mainly characterized by whatis stated in the characterizing part of claim 1.

Considerable advantages are obtained by the present invention. Thus,various embodiments of the invention are useful for making a hard maskin a TSV process to form a high aspect ratio via structure on asemiconductor substrate. Further applications include the provision of ahard mask in manufacturing of micro-electro mechanical systems andperforming as an anti-reflective coating in photolithographicpatterning. The present materials can also be used for providing a hardmask and antireflective coating in dual damascene interconnectfabrication.

Next the invention will be examined more closely with the aid of adetailed description with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in a simplified manner the process of applying a hard maskin lithographic applications;

FIG. 2 shows a similar depiction of the application of photo imageablealumina based hard mask material in lithographic applications;

FIG. 3 shows in sideview a deep via formed on silicon using polymer fromExample 1 as a hard mask in Bosch type DRIE etching;

FIG. 4 shows in sideview a deep via formed on silicon using polymer fromExample 1 as a hard mask in cryogenic DRIE etching (AR=7);

FIG. 5 shows a deep via formed on silicon using polymer from Example 3;

FIG. 6 shows the patterns obtained by photolithographic processing ofmaterial prepared in Example 5; resolution of patterns: 5 μm, 4 μm, 3μm, 2 μm, and 1 μm;

FIG. 7 shows the optical constants (index of refraction and extinctioncoefficient) as a function of wavelength for an Al_(x)O_(y) basedcoating containing copolymerized with 10% phenylsilane;

FIG. 8 shows the optical constants (index of refraction and extinctioncoefficient) as a function of wavelength for an Al_(x)O_(y) basedcoating containing copolymerized with 5% phenylsilane; and.

FIG. 9 shows the optical constants (index of refraction and extinctioncoefficient) as a function of wavelength for an Al_(x)O_(y) basedcoating containing copolymerized with 5% phenylsilane and 5%phenanthrenylsilane.

DESCRIPTION OF PREFERRED EMBODIMENTS

Based on the above discussion, a preferred embodiment encompassesprepared solutions of novel aluminum oxide polymers, and copolymer oforganosiloxanes and aluminum oxides, which can be applied in commonsemiconductor processes to produce a hard mask coating.

The compositions are synthesized from a number of inorganic ororganoaluminum precursors. The composition may also optionally includean organosilane precursor which is copolymerized with the aluminumprecursor.

The composition of the materials can be selected in such a way that ityields a material which can optionally be patterned using common photolithographic techniques or a material that absorbs light at a desiredwavelength used in photolithographic processes.

The described material is prepared by reaction of aluminum containingprecursors in a solvent with added water which causes the precursors tohydrolyze and condense to yield oligomeric and polymeric species.

According to one embodiment, a plurality of different precursors (morethan one) are used, which allows for greater flexibility in terms oftuning the material properties more suitable for its application.

The material obtained can be peptisized using inorganic or organic acid,beta-diketone or beta-diketone ester substances to impart improvedstorage stability in solution.

The backbone of the aluminum oxide polymeric material formed consists ofrepeating units of —Al—O—, which may be interrupted by optional organicacids, or beta-diketone derived ligands coordinated to the aluminum.

According to a preferred embodiment, a composition of the above kind canbe used as a hard mask in semiconductor manufacturing. It will have ahigh content of aluminum (atoms).

Furthermore the material may be peptisized using organic acids,beta-diketone or beta-diketone ester substances bearing functionalgroups that can be activated after deposition by exposure to lightpermitting patterning of the hard mask material by photolithographictechniques.

Additionally, the material may be peptisized using organic acids,beta-diketone or beta-diketone ester substances bearing functionalitieswhich absorb light at wavelengths used in photolithographic applications(193-460 nm) permitting the materials to be used in applications whereanti-reflective coatings are needed. Consequently the backbone of suchaluminum oxide polymeric material formed consists of repeating units of—Al—O— interrupted by functional groups derived from the peptisizingagents.

The described material may further be prepared by reaction of the abovealuminum precursors in combination with an organosilicon precursor in asolvent with water causing the precursor to hydrolyze and condense toyield oligomeric and polymeric species.

The use of organosilicon precursors bearing functional groups that canbe activated after deposition by exposure to light permit patterning ofthe hard mask material. Similarly, the use of organosilicon precursorswhich bear groups that absorb light at wavelengths used inphotolithographic applications (193-460 nm) permit the materials to beused in applications where anti-reflective coatings are needed.

Consequently the backbone of the aluminum oxide polymeric materialformed consists of repeating units of —Al—O— and —Si—O— which may beinterrupted by peptisizing agents mentioned for the aluminum precursors(beta-diketone, beta-diketone ester, or organic acids and organicsubstituent on the silane precursor.

The obtained solution containing the recovered reaction product from thereaction of the precursors can then be applied as hard mask layers instandard lithographic manufacturing processes on semiconductor devices.

The method which the described solutions can be applied in a multitudeof semiconductor applications and in particular in a lithographicprocess consisting of:

-   1. Application of the solution by means of spin-on, slit, spray,    roll or other coating technique used to deposit materials in liquid    phase on top of a surface of a semiconductor component or substrate.-   2. Performing an optional patterning of a dried coating by exposing    the coating to light of selected wavelength through a mask, and    development of the non-exposed areas.-   3. Allowing the applied layer to cure to obtain the hard mask in one    single layer. Followed by lithographic processes in which further    layers need to be constructed in a given device.

Turning now to preferred precursors, it can be noted that in oneembodiment, a precursor is used (in the following “precursor 1”) whichhas the general formula ofAlX_(n)(OR¹)_(3-n)wherein

-   R¹ is independently selected from the group of hydrogen, linear    alkyl, branched alkyl, cyclic alkyl, and aryls;-   X is independently chosen from a group consisting of chloro, bromo,    iodo, ester groups, in particular acyl, sulphate, sulfide, and nitro    groups,-   n is an integer which varies between 0-3.

It is further assumed that in cases where n=3, complexes such ashydrates and ether complexes are also included.

In second embodiment, another precursor (in the following “precursor 2”)is used which has the general formula of(R²)_(m)AlX_(n)(OR¹)_(2-n)wherein

-   R¹ is independently selected from the group of linear alkyl,    branched alkyl, cyclic alkyl, and aryl;-   R² is independently selected from group of carboxylic acids,    α-hydroxy carboxylic acids, carboxylic acid salts, beta-diketones,    esters and beta-ketoesters;-   X is independently chosen from a group consisting of chloro, bromo,    iodo, ester groups, in particular acyl, sulphate, sulfide, and nitro    groups; and-   m is an integer which varies between 0 and 2 and-   n is an integer which is determined by 3-m.

It is further assumed that in cases where m=0, complexes such ashydrates and ether complexes are also included.

In a third embodiment, a precursor (in the following “precursor 3”) isused which has the general formula of(R³)_(k)—Si—X_(4-k)wherein

-   R³ is independently selected from the group of linear alkyl,    branched alkyl, cyclic alkyl, alkenyl (linear, cyclic and branched),    alkynyl, epoxy, acrylate, alkylacrylate, heterocyclic,    heteroaromatic, aromatic (consisting of 1-6 rings), alkylaromatic    (consisting of 1-6 rings), cyanoalkyl, isocyanatoalkyl, aminoalkyl,    thioalkyl, alkylcarbamate, alkylurea, alkoxy, acyloxy, hydroxyl,    hydrogen and chloro-functionality, at least one of R³ is a group in    the precursor function as the functional group that can react when a    latent photoactive catalyst is activated;-   X is independently selected from the group of hydroxy, alkoxy, acyl,    chloro, bromo, iodo, and alkylamine groups; and-   n is an integer between 0 and 3.

The reaction product obtained by polymerization or copolymerizationusing one or more of the above precursors by means of hydrolysis willhave a composition consisting of precursors 1-3 (with integer n=1)described above will constitute of a general formula consisting offollowing repeating units:—[Al—O_(1.5)]_(a)—[(R²)_(m)—Al—O—]_(b)—[(R³)_(k)—Si—O_(2/3)]_(c)—whereinR² and R³ have the same meaning as above, anda, b, and c are numeric values which are based on the relative molarratio of precursors 1-3 used to obtain the above composition.

The resultant hard mask coating composition has an outstanding etchperformance after photo resist development. High aluminum content ispreferred for that use.

In cases where an organosilane precursor is applied as a comonomer inthe hydrolysis and condensation of the material a trade off exists toobtain a coating that exhibits sufficient etch selectivity and amaterial that can be patterning using photolithographic techniques.Thus, in practice an Al-content of 20 to 95% is preferred and anAl-content of 40 to 90% is more preferred.

To tailor the properties of the preferred composition, precursors 1 to 3may be chosen in such way that:

-   -   one will provide sufficient etch selectivity compared to the        substrate where the deep vias are formed and hence protect the        areas of a substrate covered with it;    -   one will provide sufficient shelf life and act to control the        molecular weight of the resultant composition;    -   one will provide sufficient adhesion to the substrate where the        deep vias are formed;    -   one will provide functional groups that can be activated by        latent catalysts which will enable patterning of the material        using photolithographic techniques; and    -   one will provide functional groups that are capable of absorbing        light at wavelengths used in photolithographic applications.

More specifically, group R¹ may be selected from a group of organicsubstituents selected from C₁₋₁₂ alkyl groups in which alkoxy, cyano,amino, ester or carbonyl functionalities may be present. The alkylgroups may optionally be halogenated bearing at least one halogen atom(fluoro, chloro, bromo or iodo-group). The described alkyl groups may belinear, branched or contain cyclic species. It is preferred that theprecursor containing a group described above may be purified bydistillation. In particular, shorter alkyl chains containing 1-6 carbonatoms are preferred. Alkyl chains containing 1-4 carbon atoms are mostpreferred.

Group R² may be selected from the group of carboxylic acids, α-hydroxycarboxylic acids, carboxylic acid salts, beta-diketones, esters orbeta-ketoesters selected from from C₁₋₁₂ alkyl groups in which halogen,unsaturated, and aromatic functionalities may be present. It ispreferred that the precursor 2 containing a group described above may bepurified by distillation or prepared in such way that the total metalion content is lower than 500 ppb, preferably lower than 50 ppb. Inparticular, alkyl chains as short as possible containing 3-7 carbonatoms are preferred.

Alkyl chains containing 4-6 carbon atoms are most preferred. Morepreferred are embodiments containing organic acids, beta-diketones, orbeta-diketo esters consisting of compounds which also contain afunctionality which may be polymerized using photolithographictechniques such as acryl, alkylacryl, acrylate, alkylacrylate, and epoxyfunctionalities. Such functional compounds may contain 5-12 carbonatoms. Alkyl chains containing 6-10 carbon atoms are more preferred.Preferred embodiments also include organic acids, beta-diketones orbeta-diketoesters containing functional groups that are capable ofabsorbing light of wavelengths used in photolithographic processing.Particularly preferred light absorbing embodiments are aromatic orpolyaromatic (containing 2-6 aromatic rings) that have substitutentswhich at least one is an organic acid, a beta-diketone or abeta-diketoester.

Group R³ may be selected in such way that further reactions may takeplace during heating permits the material to be further densified i.e.crosslinked. More preferred are those functional groups which permit theuse of latent catalysts which can be activated in standard lithographicprocesses to yield coatings that can be patterned. Such substituentsinclude C₁₋₁₂ alkenyl, C₁₋₁₂ alkynyl, C₁₋₁₂ acrylate, C₁₋₁₂alkylacrylate, and C₁₋₁₂ epoxy groups. Preferred alkenyl and alkynylgroups consist of 1-6 carbon atoms such as vinyl, allyl, butenyl,pentenyl, hexenyl, butadienyl, pentadienyl, hexadienyl, acetyl,propargyl, butynyl, pentynyl and hexynyl. Acryl, alkylacryl, acrylate,alkylacrylate substituents consist preferably of 1-7 carbon atoms, whichmay be interrupted by a heteroatom. More preferred are those functionalgroups which permit the use of latent catalysts which can be activatedin standard lithographic processes to yield coatings that can bepatterned. Preferred acrylate substituents contain methyl- and ethylacrylate. Preferred alkylacrylate substituents consist of methylmethacrylate, methyl ethylacrylate, ethyl methacrylate and ethylethacrylate. Epoxy substituents consist preferably of 1-8 carbon atoms,which may be interrupted by a heteroatom. Preferred epoxy substituentsare for example glycidoxypropyl, and ethyl-(3,4-cyclohexylepoxy). Theuse of substitutents containing the functionalities alkenyl, alkynyl,epoxy, acrylate, and alkylacrylate provides the material to be aphotopatternable material when used in combination of latent catalyststhat may be activated by exposure to light of desired wavelength.

Group R³ may also be selected in such way that the resulting reactionproduct has the capability of absorbing light at wavelengths used inphotolithographic processing. Such substituents include C₁₋₁₂ alkenyl,C₁₋₁₂ alkynyl, C₁₋₁₂ acrylate, C₁₋₁₂ alkylacrylate, C₆-C₃₆ aromatic andC₆-C₃₆ heteroaromatic groups. More preferred are aromatic compounds thatcan be purified by distillation. The preferred aromatic groups maycontain substitutents such as C₁₋₆ alkyl, C₁₋₆ acyl, C₁₋₆ alkoxy, nitro,amino and halogen functionalities. Of particular preference are suchgroups which can be independently selected and employed jointly in orderto adjust the optical properties, such as the index of refraction andthe extinction coefficient, of the material at a desired wavelengthafter its cure on a semiconductor substrate.

Unambiguous examples of suitable compounds for precursor 1 includealuminum hydroxide, aluminum methoxide, aluminum ethoxide, aluminumisopropoxide, aluminum sec-butoxide, aluminum chloride (and otherhalogenated aluminates including their complexes and hydrates), aluminumnitrate (including its hydrates), aluminum sulfate (including itshydrates) and combinations of alkoxy and halogenated aluminum precursorssuch as chlorodiisopropoxyaluminum, as well as any other precursors thatconsist of functional groups that can be cleaved off the aluminum withease during a hydrolysis/condensation polymerization.

Unambiguous examples of suitable precursors for precursor 2 includerelated aluminum precursors discussed above in which an organic group R²is included as a covalent bond or through coordination. Such compoundsare 2,4-pentadione, 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione,3-propyl-2,4-pentanedione, 3,3-dimethyl-2,4-pentanedione,3,5-heptanedione, 4-methyl-3,5-heptanedione, 4-ethyl-3,5-heptanedione,4-propyl-3,5-heptanedione, 4,4-dimethyl-3,5-heptanedione,6-methyl-2,4-heptanedione, 1-phenyl-1,3-butanedione,1,1,1-trifluoro-2,4-pentanedione, 3-chloro-2,4-pentanedione,2-acetylcyclopentanone, 2-acetylcyclohexanone, methyl acetoacetate,ethyl 2-methylacetoacetate, methyl 2-ethylacetoacetate, ethylacetoacetate, ethylpropionylacetate, methyl 3-oxovalerate, isopropylacetoacetate, ethyl 2,4-dioxovalerate, methyl 3-oxohexanoate, methyl4-methyl-3-oxovalerate, allyl acetylacetoacetate,2-methyl-3-oxo-pent-4-enoic acid methyl ester, methyl4-methoxyacetoacetate, methyl 2-hydroxy-2-methyl-3-oxobutyrate, methyl2-oxocyclopentanecarboxylate, methyl 2-oxocyclohexanecarboxylate, ethyl2-oxocyclopentanecarboxylate, ethyl 2-oxocyclohexanecarboxylate, ethyl2-ethylacetoacetate, methyl 3-oxoheptanoate, isobutyl acetoacetate,methyl 4,4-dimethyl-3-oxopentanoate, ethyl isobutyrylacetate, C₁₋₁₂alkyl carboxylic acids, C₁₋₁₂ unsaturated carboxylic acids, and C₁₋₁₂aromatic carboxylic acids.

Unambiguous examples of suitable precursors 3, which can be activatedusing latent photo active catalysts includemethacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane,methacryloxypropyltripropoxysilane,methacryloxypropyltris(isopropoxy)silane,methacryloxypropyltrichlorosilane,methacryloxypropylmethyldimethoxysilane,methacryloxypropylmethyldiethoxysilane, acryloxypropyltrimethoxysilane,acryloxypropyltriethoxysilane, acryloxypropyltripropoxysilane,acryloxypropyltris(isopropoxy)silane, acryloxypropyltrichlorosilane,acryloxypropylmethyldimethoxysilane, acryloxypropylmethyldiethoxysilane,methylmethacryloxypropyltrimethoxysilane,methylmethacryloxypropyltriethoxysilane,methylmethacryloxypropyltripropoxysilane,methylmethacryloxypropyltris(isopropoxy)silane,methylmethacryloxypropyltrichlorosilane,methylmethacryloxypropylmethyldimethoxysilane,methylmethacryloxypropylmethyldiethoxysilane,methylacryloxypropyltrimethoxysilane,methylacryloxypropyltriethoxysilane,methylacryloxypropyltripropoxysilane,methylacryloxypropyltris(isopropoxy)silane,methylacryloxypropyltrichlorosilane,methylacryloxypropylmethyldimethoxysilane,methylacryloxypropylmethyldiethoxysilane,glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane,glycidoxypropyltripropoxysilane, glycidoxypropyltris(isopropoxy)silane,glycidoxypropyltrichlorosilane, glycidoxypropylmethyldimethoxysilane,glycidoxypropylmethyldiethoxysilane,ethyl-(3,4-cyclohexylepoxy)trimethoxysilane,ethyl-(3,4-cyclohexylepoxy)triethoxysilane,ethyl-(3,4-cyclohexylepoxy)tripropoxysilane,ethyl-(3,4-cyclohexylepoxy)tris(isopropoxysilane,ethyl-(3,4-cyclohexylepoxy)trichlorosilane,ethyl-(3,4-cyclohexylepoxy)methyldimethoxysilane, andethyl-(3,4-cyclohexylepoxy)methyldiethoxysilane.

Unambiguous examples suitable precursors 3, which can be used to tunethe optical properties of the resultant material arephenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane,phenyltris(isopropoxy)silane, phenyltrichlorosilane,naphthyltrimethoxysilane, naphthyltrimethoxysilane,naphthyltripropoxysilane, naphthyltris(isopropoxy)silane,naphthyltrichlorosilane, anthracenyltrimethoxysilane,anthracenyltriethoxysilane, anthracenyltripropoxysilane,anthracenyltris(isopropoxy)silane, anthracenyltrichlorosilane,phenanthrenyltrimethoxysilane, phenanthrenyltrimethoxysilane,phenanthrenyltripropoxysilane, phenanthrenyltris(isopropoxy)silane,phenanthrenyltrichlorosilane, pyrenyltrimethoxysilane,pyrenyltrimethoxysilane, pyrenyltripropoxysilane,pyrenyltris(isopropoxy)silane, pyrenyltrichlorosilane,fluorenyltrimethoxysilane, fluorenyltrimethoxysilane,fluorenyltripropoxysilane, fluorenyltris(isopropoxy)silane, andfluorenyltrichlorosilane. These examples of aromatic substituents may beattached to the silicon from any site of the molecule (e.g. 1-naphthyl,2-naphthyl) and may additionally bear functional groups such as alkyl,acyl, alkoxy, nitro, amino, or halogen atoms on the aromatic ring.

Polymers obtained from the above-mentioned aluminum and silaneprecursors which can be hydrolyzed and copolymerized with each other andcontain functional groups that can be further reacted upon activation ofa latent, photo-active catalyst yield coatings which can be used hardmasks in photolithographic processes.

The function of above precursor groups are follows in general:

Precursor 1—provide high aluminum content for hard mask coating;

Precursor 2—impart to sufficient shelf-life and optionally a patternedprofile, obtained with standard lithographic processes or provide thematerial a light absorbing function;

Precursor 3—impart to a patterned profile, obtained with standardlithographic processes a light absorbing function.

Preferred compositions in molar percentages of the precursors used are:

Precursor 1: 50-99;

Precursor 2: 5-80; and

Precursor 3: 1-40.

Particularly preferred molar percentages are: Precursor 1: 50-90;Precursor 2: 10-70; and Precursor 3: 5-30.

The manufacturing of the preferred embodiments occurs by performing anacid or base catalyzed hydrolysis and condensation reaction of 1-4aluminum precursors, preferably 1-2 of aluminum precursors, optionallycopolymerized with a silane precursor in a solvent or a combination ofsolvents. Suitable solvents to perform the hydrolysis and condensationstep are acetone, tetrahydrofuran, 2-methyltetrahydrofuran, butanone,cyclopentanone, cyclohexanone, alcohols (methanol, ethanol, propanol),propylene glycol derivatives [in particular propylene glycol monomethylether acetate (PGMEA), propylene glycol monomethyl ether (PGME),propylene glycol monoethyl ether (PGEE), propylene glycol monopropylether (PNP)], ethylene glycol derivatives and methyl tert-butyl ether.Mixtures consisting of two or more of these solvents may also beemployed. The weight ratio of the solvents to the precursors in thesynthesis may be varied from 20:1 to 0.5:1. A weight ratio of thesolvents to the precursor preferably varies in the range from 10:1 to1:1. The amount of water used in the acid or base catalyzed hydrolysisand condensation of the precursors may vary considerably. The use of 1-3molar equivalents of water per hydrolyzing functional group, a polymericmaterial is formed, while a 5-15 time excess per weight yields colloidalsuspension of polycationic aluminum species. To prepare a polymericmaterial a 1-2 molar equivalents of water based on hydrolyzingfunctional groups is preferred while a 5-10 excess by weight ispreferred when colloidal polycationic aluminum species are prepared. Thereaction mixture may be stirred at room temperature or brought to refluxfor 1-48 hours, preferably 1-24 hours during synthesis.

Once the hydrolysis and condensation step is complete, excess reagents(water), reaction byproducts (such as methanol, ethanol, isopropanol,2-butanol) and the solvent may be removed under reduced pressure. Duringthe removal of volatiles another solvent, possessing a higher boilingpoint and more desirable properties in terms of its use in furthermanufacturing steps of the polymer solution may be introduced. Onceremoval of volatiles is complete, the obtained material may then beformulated to its final composition or be subjected to a molecularweight adjustment step. This molecular weight increase step is carriedout at elevated temperatures ranging from 50° C. to 180° C. The use of60-120° C. during the molecular weight adjustment step is morepreferred. After the molecular weight increase step, the material may beformulated to its final composition.

The formulation consists of diluting the material using a solvent orcombinations of these. Solvents used in final formulation are chosen tomaximize the uniformity of the coating and storage stability. For goodspin coating properties, solvents of higher boiling points andviscosities may be preferred (e.g. PGMEA). Stabilizing solvents may beadded to the product to improve storage stability. Such solvents possessmost frequently contain hydroxyl groups as these either coordinate tothe polymeric OH's or react with these appreciably without affectingadversely on the properties of the cured film. Additives, such assurfactants (by e.g. BYK-Chemie, 3M and Air Products), photo- orthermally latent catalysts (e.g. Rhodorsil 2074 and Irgacure 819), andfurther peptisizing agents may be added. The surfactant may improvewetting of the substrate which is to be coated and hence improves theuniformity of the resultant film. Generally, non-ionic surfactants arepreferred. The peptisizing agent provides improved shelf life to theproduct. The peptisizing agent may consist of inorganic or organicacids, or beta diketone derivatives.

After coating, drying and curing, a film consisting of an alumina oraluminosiloxane core with carbon based functionalities is formed. Thecure temperature is preferred to be at most 400° C., but more preferredto be 250° C. A single cure step is preferred. The resultant cured filmthickness is dependent on the dilution of the polymer solution andranges usually between 10-1000 nm. The refractive index of the film isbetween 1.4-1.7 when measured using a tool at a wavelength of 632 nm.The film is preferred to possess a thermal stability up to 400° C. and aminimal out gassing of volatile components to reduce adverse effectsupon subsequent coatings or processes used in semiconductor fabrication.

FIG. 1 shows for a lithographic process: deposition of hard mask onsubstrate to be patterned, deposition of photoresist, exposure ofphotoresist, developing the photoresist, etching the hard mask removalof photoresist, etching pattern to desired material and removal of thehard mask. According to the embodiment shown in that figure, thedescribed materials are applied to a substrate 10 by means of spincoating. Other coating methods may also be applicable if the applicationin which the described materials are used in requires this. Aftercoating, the described material is then cured to give hard mask 20. Aphoto resist 30 is then applied on top of the hard mask and processed(exposed and developed) to yield a pattern where the hard mask isexposed. The pattern is then transferred to the hard mask by dry or wetetching. Prior to the etching of the substrate through the openedpatterns generated on the hard mask, the photo resist may be removedfollowing common practices which are well known to those familiar withthe art. Finally, after the etching of deep, high aspect ratio vias onthe substrate, the hard mask is removed using dry or wet cleaningprocedures. However, a hard mask material which is patternedsimultaneously during photo resist development may be preferred if thepattern is transferred in a sufficient manner by this techniques. Thisoccurs when the hard mask layer develops jointly with the photo resistand may result in considerable saving in time and cost when a separatepattern transfer step by wet or dry etching is not needed for the hardmask.

FIG. 2 shows a substrate 10, and photo imageable hard mask 20. Includesdeposition of hard mask on substrate to be patterned, exposure ofpatternable hard mask, developing the soluble part of the exposed hardmask, etching pattern to desired material and removal of hard mask.

Examples 1 to 3 describe materials prepared and cured in this way. Thesewere subjected to common DRIE etching conditions (Table 1). Their etchselectivities to Si are shown in Table 2.

Standard pattern formation of the alumina coatings were obtained using acommon pattern transfer employing a photoresist. Deep vias were formedusing the same DRIE conditions without degradation on the Si protectedby the alumina hard mask (FIGS. 3-5).

A more preferred method to yield patterns on the hard mask, is toprepare a hard mask which itself can be patterned by photolithographictechniques. In such event, considerable savings in manufacturing timeand cost can be achieved. The patterned hard mask can be obtainedthrough techniques for negative tone photo resist (FIG. 2) whichincludes the coating of a substrate (10), drying, exposure of the hardmask (20) through a mask, post exposure bake, development of non-exposedareas and final cure. After etching, the hard mask is removed using dryor wet cleaning procedures. Similarly, the patterned hard mask may alsobe obtained through techniques for positive tone photo resists. The useof a latent radiation sensitive catalyst provides such a possibility tocrosslink the alumina based hard mask. Such latent catalysts decomposeupon exposure to radiation to give an acid or radical which cause thefunctional groups to undergo reactions. The cure of the exposed partsmay occur due to condensation reactions catalyzed by the strong acidliberated by exposure. The cure may also be achieved by other means,providing that functional groups which can undergo acid or radicalinitiated polymerization reactions are present in the composition of thepolymer. As described earlier, the use of precursors 2 or 3 containingreactive R² or R³ substituents such as alkenyl, alkynyl, epoxy,acrylate, and alkylacrylate may provide the material to be cured throughthe latter mechanism when used in combination with catalysts that can beactivated by exposure to light of desired wavelength. In a negative toneprocess, the regions through which light passes to the film will becured when irradiation is carried out through a patterned mask. Thenon-exposed areas can then be dissolved in the aqueous developerresulting in a transfer of the pattern on the mask to the film. Prior tothe exposure of the film to radiation a heating step is carried out toremove the volatile components of the formulation. This temperature isbetween 50-170° C., preferably between 70-150° C. not to cause prematurecross-linking of the resin which may result in the non-exposed areas tobe insoluble to developers. Similarly, after the exposure a postexposure bake is carried out to accelerate the reactions initiated bythe latent catalyst. For a positive tone process, the image is inpractice reversed when compared to the negative tone process. Hence, theexposed regions of a positive tone material dissolve in the developer.

Patternable materials may also be obtained when a precursor 2 bears areactive functionality that may be polymerized initiated by a radiationsensitive latent catalyst. For those known to the art, this and theabove provides a possibility to form patterned structures when the lightis directed through a mask and a stepper.

The amount of precursors 2 or 3 containing reactive R² or R³substituents is important in order to achieve patternable materials. Ithas been found that 10% of a reactive precursor 3 was insufficient togive a patternable material (Example 4). Similarly it was found that anexcess or lack of sufficient amount of precursor 2 resulted in no orless favorable pattern formation (Example 9).

In the process flow of forming deep high aspect ratio vias, the removalof the alumina hard mask can also be omitted. Hence, the alumina basedmaterials are expected to possess CTE values close to that of silicon.Such similarity in CTE values are important in non-sacrificialapplications of the material to minimize mechanical stress created orthermal mismatches experienced in a device during and after variousmanufacturing steps which involve elevated temperatures.

Alumina based hard mask coatings containing groups which are capable ofabsorbing light may be used in advanced lithographic applications wherenarrow line widths are formed. The light absorbing groups may beintroduced as substituents of silicon (R³ in precursor 3) or as acoordinating ligand to aluminum (R² in precursor 2). In suchlithographic applications, the ability to control the optical propertiessuch as index of refraction and the extinction coefficient of the filmare of great importance. Examples 6-8 describe the synthesis ofmaterials where the optical constants can be adjusted by controlling thesubstituent and its content in the alumina based hard mask. The valuesfor the optical constants for various wavelengths used in lithographicapplications are shown in FIGS. 7-9. For those known to the art, theindex of refraction and the extinction coefficient can be adjusted bychoosing the light absorbing compounds and their content in the givenhard mask composition. Hence, the light absorbing moieties are notlimited to the groups given in the examples and other moieties known toabsorb in a desired wavelength can be used to tune the optical constantssuitable for the particular application.

Based on the above, in one embodiment, the present method comprisessteps in which the hard mask is patterned using lithography and etch.This embodiment comprises in combination the steps of

-   -   depositing a hard mask material by means of spin, slit, spray or        other method suitable for application of materials in solution;        curing of the hard mask material at desired temperatures;    -   depositing, patterning and developing a photoresist on said hard        mask to expose desired regions of the hard mask;    -   transferring the pattern from mentioned photoresist to specified        exposed regions of the given hard mask by means of selective        etching;    -   optionally removing the said, patterned photoresist using        conventional etching techniques; and    -   transferring the pattern from the mentioned hard mask and        photoresist to the given substrate using etching processes.

In the last step, preferably etching processes are used which are highlyselective and which do not cause damage on the non-exposed areas of thesubstrates due to undesired reactions through the hard mask layer.

In one embodiment, the hard mask composition contains at least —Al—O—and —Si—O— resin core interrupted by organic substituents. In anotherembodiment, the hard mask composition contains at least —Al—O— resincore interrupted by organic substituents.

The structures produced can, in one embodiment, exhibit etch selectivitybetween the hard mask and a substrate is at least 500:1. However, it canvary in a much broader range also, of about 10,000:1.

In one embodiment, the curing of the coating is carried out on ahotplate at a temperature of 200-400° C., preferably at 200-300° C. Inanother embodiment, the curing of the coating is carried out in afurnace at a temperature of 400-1000° C., preferably at 400-650° C.

In any of the above embodiments, a developer comprising or consisting ofa diluted TMAH solution can be used.

The present process according to the present invention can be used inembodiments wherein via structures having high aspect ratios are aimedat. Thus in one embodiment, the process yields high aspect ratio viastructure on a semiconductor substrate with aspect ratio at least 5:1 ormore preferably higher 50:1. In another embodiment, the process yieldshigh aspect ratio via structure on a semiconductor substrate with viadepth of 100 μm, preferably more than 200 μm.

As apparent, the invention can be used in various methods of performingsemiconductor lithography, etch and via formation process using aprotective alumina based hard mask layer that is capable of absorbinglight used in lithographic processing.

In another embodiment, the present invention comprises a method offorming a thin film hard mask on a substrate comprising the steps of:

-   -   reacting the substrate surface with a chemical composition        obtained by hydrolyzing a first metal oxide precursor with a        hydrolyzing catalyst in the presence of a peptisizer and a        solvent,    -   optionally further co-reacting the first metal oxide precursor        with a second metal or metalloid oxide precursor,    -   to produce a solution of an intermediate oligomeric or polymeric        material;    -   optionally performing a solvent exchange process for the        intermediate chemical solution;    -   heating the thin film hard mask at elevated temperature to        undergo solvent removal partial or complete cross linking        reaction; and    -   processing the thin film hard mask by a semiconductor        lithographic method.

In the method, as apparent from the above, the first metal oxideprecursor can be selected from the group of aluminum chloride, aluminumalkoxide, aluminum nitrate, aluminum acetate, aluminum acetoacetateprecursor and combinations thereof.

In one embodiment, the intermediate oligomeric or polymeric thin filmhard mask can be cured at the elevated temperature can lithographicallypatterned by using negative to lithography process.

In any of the above embodiments, the R³ group is preferably a mixture ofphenyl and a polyaromatic compound. By this embodiment to obtainpredetermined optical properties by lithographic pattering.

More particularly, examples of applications in which the materials workas hard masks include:

-   -   A. Hard mask compatible with redistribution, wafer bumping        dielectrics or passivation layers. In particular the hard mask        can be coated on a dielectric (organic, hybrid or inorganic)        material, normally patterned in a lithographic process and        afterwards removed with mild chemical stripping chemical without        removing or damaging the dielectric film. The stripping        selectivity can be adjusted with organic additives such as acac        during the polymerization.    -   B. Hard mask containing an organic group having absorption at        lithographic process wavelengths (typically 193 nm-460 nm). This        light attenuation component provides the material to be        simultaneously used in an anti-reflection coating function when        it used in conjugation with photo resist lithographic        patterning.    -   C. Hard mask compatible with second transfer layer material such        as spin-on-carbon (SOC) polymer. The hard mask can be coated on        SOC polymer to enhance total stack selectivity. After via        patterning the stack can be removed with mild wet chemical        removal.

D. Hard mask and etch stopper in dual damascene interconnectfabrication. In dual damascene process, SiCxNy, or SiOxNy are used asetch stopper that separate Cu levels. By replacing conventional etchstopper with described materials, via height can be reduced thusreducing the total Cu line length.

-   -   E. Hard mask for micro-electro-mechanical systems (MEMS)        manufacturing. The described materials can be patterned into        desired shapes using photolithographic techniques. The vertical        dimension is adjusted by etching of the substrate.

Potential applications of the materials may also include other than inthe formation of deep, high aspect ratio structures. Such specificexamples include:

-   A. Passivation applications where high mechanical properties are    required.-   B. For shallow trench isolation for both logic and memory devices.    The described materials may also be used as a filling material for    the shallow isolated trenches.

TABLE 1 Parameters used during the 10 min etch tests carried out forreported values. Gas Power Cycle Time Etch Passivation Etch EtchPassivation Passivation Temp. Etch Passivation SF6/O2 C4F8 Coil PlatenCoil Platen Platen (sec.) (sec.) (sccm) (sccm) (W) (W) (W) (W) (C.) 12 7130/13 110 900 14 800 0 24

The following non-limiting examples illustrate the invention.

Example 1

Aluminum isopropoxide (15 g) and THF (52.5 g) were placed in a roundbottom flask equipped with a magnetic stir bar and a reflux condenser.Acetoacetonate (acac, 7.35 g) was added dropwise once the aluminumisopropoxide had dissolved. The mixture was stirred at room temperaturefor 1 h and then methanol (52.5 g) was slowly added, followed by amixture of 0.01M HNO₃ (5.29 g) and isopropanol (5.29 g). Aftercompletion of the additions, the reaction mixture was allowed to refluxfor 16 h by placing the flask in an oil bath at 100° C. When thereaction mixture had cooled to room temperature, volatiles were removedunder reduced pressure until 35.4 g of the mixture remained. 2-Butanone(95 g) was added and the evaporation step was repeated until 33.7 gmaterial remained. The obtained solution was then formulated with2-butanone and methanol to produce a solution that was spin coated on asubstrate. A coating having an index of refraction of 1.50 and athickness of 81 nm was obtained after a 200° C. cure.

Example 2

The above was repeated using acac (3.68 g). The obtained solution wasformulated with 2-butanone and methanol to produce a solution that wasspin coated on a substrate. A coating having an index of refraction of1.44 and a thickness of 108 nm was obtained after a 200° C. cure.

Example 3

Aluminum isopropoxide (3 g) and ethanol (11.25 g) were placed in athree-necked round bottom flask equipped with an overhead stirrer and areflux condenser. The flask was immersed in an oil bath at 100° C. After5 min, a mixture of deionized water (22.5 g) and 60% HNO₃ (0.14 g) wasslowly added and allowed to reflux for 24 h. The reaction mixture wasfurther formulated using deionized water and ethanol. The solution wasspin coated on a substrate and cured at 200° C. to yield a coatinghaving an index of refraction of 1.50 and a thickness of 93 nm.

Example 4

The preparation of Example 2 was repeated. After removal of volatiles,42.5 g of material having a solid content of 18.1% was obtained. In aseparate reaction, glycidoxypropyl-trimethoxysilane (5 g), acetone (10g) and 0.01M HNO₃ (1.14 g) was allowed to stir at room temperature for24 h to give a glycidoxypropylsilane based hydrolysate. The aluminumcontaining solution (3 g) was mixed with 0.44 g of theglycidoxypropylsilane based hydrolysate to give a copolymer with molarratio of Al:Si equal to 9:1. The homogenous mixture was heated at 60° C.for 30 min. The material was formulated with photo acid catalysts,coated and exposed through a mask. After development, no patterns wereobtained.

Example 5

The procedure of Example 4 was repeated. The molar ratio of Al:Si wasset to 7.5:2.5. The aluminum containing solution (16.6 g) was mixed with7.3 g of the glycidoxypropylsilane based hydrolysate. The homogenousmixture was heated at 75° C. for 45 min and the obtained solution wasformulated with cyclohexanone and photo acid generators. The solutionwas spin coated on a substrate and cured at 200° C. to yield a coatinghaving an index of refraction of 1.51 and a thickness of 152 nm. Thematerial could be patterned using photolithographic techniques (FIG. 5).

Table 2 shows the properties and etch rate results of the materialsprepared by the examples below in comparison with a standard photoresist. Etch rate 1 based on Bosch type and etch rate 2 based oncryogenic DRIE processes.

TABLE 2 Cure temperature Etch rate 1 Etch rate 2 Material [° C.] RI[nm/min] [nm/min] Shipley SPR700 31.1 Example 1 400 1.553 0.4 0.2Example 2 400 1.489 0.9 Example 3 400 1.502 0 Example 5 200 1.510 2.5Example 5 400 1.510 1.1

Example 6

The preparation of Example 2 was repeated. After removal of volatiles,263.97 g of aluminum oxide containing material having a solid content of19.76% was obtained. In a separate reaction, acetone (49.76 g) andphenyltrimethoxysilane (51.76 g) were place in a round bottom flaskequipped with a Teflon covered magnetic stir bar and a reflux condenser.Nitric acid (0.01M, 14.10 g) was drop wise added to the flask and thereaction mixture was then allowed to stir at room temperature for atleast one hour. Of the aluminum oxide solution, 10.0 g was placed into a50 ml round bottomed flask equipped with a Teflon covered magnetic stirbar and a reflux condenser. A 10 mol-% phenylsiloxy containing aluminumoxide mixture was obtained by drop wise addition of 0.92 g of thephenylsiloxy hydrolysate. The mixture was stirred at room temperaturefor 5 min and then placed in an oil bath at 75° C. for 10 min. A highlyviscous, gel like material was obtained and stored at room temperatureovernight. Then n-propoxy propanol (PNP, 15 g) was added and 6 drops ofconcentrated nitric acid was added while the mixture was vigorouslystirred. The material was then filtered and spin coated at 2000 rpm andcured at 200° C. for 5 min to obtain a film having an index ofrefraction of 1.5171 and a thickness of 134 nm

Example 7

The preparation of Example 6 was repeated. A 5 mol-% phenylsiloxycontaining aluminum oxide mixture was obtained by drop wise addition of0.43 g of the phenylsiloxy hydrolysate. The mixture was stirred at roomtemperature for 5 min and then placed in an oil bath at 75° C. for 30min. A highly viscous, gel like material was obtained and stored at roomtemperature overnight. Then cyclohexanone was added, the material wasfiltered and spin coated at 2000 rpm and cured at 200° C. for 5 min toobtain a film having an index of refraction of 1.4555 and a thickness of427 nm

Example 8

The preparation of Example 6 was repeated. A 5 mol-% phenylsiloxy and 5mol-% phenanthrenylsiloxy containing aluminum oxide mixture was obtainedby drop wise addition of 0.20 g of the phenylsiloxy hydrolysate and 0.79g of a phenanthrenylsiloxy hydrolysate prepared in a similar manner asthe phenylsiloxy hydrolysate. The two hydrolysates were simultaneouslyadded drop wise to the aluminum oxide containing solution. The mixturewas stirred at room temperature for 5 min and then placed in an oil bathat 75° C. for 20 min. A highly viscous, translucent, gel like materialwas obtained and stored at room temperature overnight. Then n-propoxypropanol (PNP, 15 g) was added and 6 drops of concentrated nitric acidwas added while the mixture was vigorously stirred. The material wasthen filtered and spin coated at 2000 rpm and cured at 200° C. for 5 minto obtain a film having an index of refraction of 1.5456 and a thicknessof 194 nm.

TABLE 3 Values of optical constants for alumina based hard masks inExamples 6-8 193 nm wavelength 248 nm wavelength Example # N k n k 61.629 0.26 1.589 0.003 7 1.613 0.11 1.491 0.001 8 1.629 0.24 1.555 0.132

Example 9

Aluminum isopropoxide (5 g) and IPA (15 g) were placed in a round bottomflask equipped with a magnetic stir bar and blanketed with argon. Ethylbenzoyl acetate (1.95 g) was added drop-wise once the aluminumisopropoxide had dissolved. The mixture was stirred at room temperaturefor 5 minutes before the addition of hydrochloric acid (10M, 0.01 g) andwater (0.38 g). After completion of the additions, the reaction mixturewas allowed to stir at room temperature for 16 h. The solution having asolid content of 31% was then formulated with Irgacure 819 (5 wt %) andfiltered (0.1 μm) before spin-coating. The coated material could bepatterned by photolithographic techniques to yield a positive toneimage.

Although various embodiments of the present invention have beendescribed and shown, the invention is not restricted thereto, but mayalso be embodied in other ways within the scope of the subject-matterdefined in the following claims.

What is claimed is:
 1. A method of forming a protective hard mask layeron a substrate in a semiconductor etch process, comprising the step ofapplying by solution deposition on the substrate a solution or colloidaldispersion of a polymer, said solution or dispersion being obtained bythe steps consisting of hydrolysis and condensation of monomers ofaluminum isopropoxide in a solvent or a solvent mixture in the presenceof water and a catalyst to form an alumina polymer, followed bycombining the alumina polymer with a silane polymer formed by hydrolysisand condensation of glycidoxypropylsilane, wherein the molar ratio ofAl:Si is 7.5:2.5.
 2. The method according to claim 1 wherein the curetemperature is 400° C.